Teratogenesis is a medical term from the Greek, literally meaning monster making. It has gained a more specific usage for the development of abnormal cell masses during fetal growth (see pregnancy), causing physical defects in the fetus.
There are a large number of teratogenic materials, such as Diethylstilbestrol and Thalidomide. Rubella (German measles) virus is also teratogenic, as is use of large amounts of alcohol during pregnancy (Fetal Alcohol Syndrome). Some acne medications (for instance, Accutane®) contain the active ingredient isotretinoin (13-cis-retinoic-acid), which is a strong teratogen. Just a single dose taken by a pregnant woman may result in serious birth defects. Because of this effect, most countries have systems in place to ensure that it is not given to pregnant women, and that the patient is aware how important it is to prevent pregnancy during and at least one month after treatment.
The term teratogenesis refers to the production of congenital malformations such as cleft lip and/or palate, anencephaly, or ventricular septal defect, which are medically serious abnormalities present at birth. The term derives from teratology, the study of the frequency, causation, and development of congenital malformations--misleadingly called birth defects.
It could be a prescribed medication, a street drug, alcohol use, or a disease present in the mother which could increase the chance for the baby to be born with a birth defect.
Teratogens are thought to have the ability to affect the fetus about 10 to14 days after conception.
If a teratogen has the potential to interfere with the closure of the neural tube, for example, the exposure to the teratogen must occur in the first 3.5 to 4.5 weeks of the pregnancy, since this is when the neural tube is closing.